Bring a large pot of salted water to a boil. Add the linguine and cook according to package instructions until al dente, about 8-10 minutes. Reserve a cup of pasta water, then drain and set the linguine aside.

In a large skillet, melt 4 tablespoons of unsalted butter over medium heat until bubbling and golden.

Add cleaned and sliced squid to the skillet, sauté for 2-3 minutes until just opaque and tender.

Mix in thinly sliced red onion and crushed red pepper, cooking for another 2-3 minutes until onions soften.

Drizzle in lemon juice and toss in the cooked linguine, coating it with the sauce. Add reserved pasta water if needed.

Char lemon wedges cut-side down in the skillet for about 2 minutes until caramelized.

Transfer to plates, garnish with parsley and serve with charred lemon wedges.